Krebs on Security

In-depth security news and investigation

Posts Tagged: Pushdo

Hardly a week goes by when I don’t hear from some malware researcher or reader who’s discovered what appears to be a new sample of malicious software or nasty link that invokes this author’s name or the name of this blog. I’ve compiled this post to document a few of these examples, some of which are quite funny.

Source: Exposedbotnets.com

Take, for example, the login panel for “Betabot“: Attempt to log in to this malware control panel with credentials that don’t work and you’ll be greeted with a picture of this author, accompanied by the following warning: “Enter the correct password or I will write a 3-part article on this failed login attempt.”

The coders behind Betabot evidently have several versions of this login panel warning: According to a threat intelligence report being released tomorrow by RSA, the latest iteration of this kit uses the mugshot from my accounts at Twtter (follow me!) and Facebook (like it!).

As first detailed by Sophos’s award-winning Naked Security blog, the code inside recent versions of the Redkit exploit kit includes what appears to be a message blaming me for…well, something. The message reads: “Crebs, its [sic] your fault.”

Text string inside of the Redkit exploit kit. Source: Sophos

The one I probably hear about most from researchers is a text string that is built into Citadel (PDF), an offshoot of the ZeuS banking trojan botnet kit that includes the following reference: “Coded by BRIAN KREBS for personal use only. I love my job and my wife.”

A text string within the code of the Citadel trojan. Source: AhnLab

Those are just the most visible examples. More commonly, if Yours Truly is invoked in the name of cybercrime, it tends to show up in malicious links that lead to malware. Here are a few just from the past couple of weeks:

Previous stories in my Pharma Wars series have identified top kingpins behind the some of the biggest spam botnets. Today’s post does that and more, including never-before-published information on “Google,” the lead hacker behind the world’s busiest spam botnet — Cutwail.

December 2011 spam stats from M86Security

For many years, Cutwail has been among the top three most prolific spam botnets. With the recent takedown of the Rustock botnet, Cutwail now is the top spam bot; according to M86 Security, versions of Cutwail are responsible for about 22 percent of the daily spam volumes worldwide.

Security researchers have extensively dissected the technical machinery that powers Cutwail (a.k.a. “Pushdo” and “Pandex”), but until now little has been published about the brains behind it. Krebs On Security has learned that the individual principally responsible for developing and renting this crime machine to other miscreants was a top moneymaker for SpamIt, until recently the world’s largest rogue Internet pharmacy affiliate program.

By the time he joined SpamIt in early 2007, the hacker named Google had already spent several years fine-tuning his spam botnet. Just months prior to its closure in Oct. 2010, SpamIt was hacked, and its customer and affiliate data leaked online. The data shows that Google used close to a dozen affiliate accounts at SpamIt, and made nearly $175,000 in commissions advertising SpamIt’s rogue online pharmacies with the help of Cutwail.

But Google would make far more money renting his botnet to other spammers, and SpamIt affiliates quickly became his biggest client base. Interestingly, the proprietors of SpamIt initially asked for Google’s help not to spam rogue pharmacies, but to jump-start a new affiliate program called Warezcash to sell “OEM” software — mostly pirated copies of Microsoft Windows and other high-priced software titles.

That relationship is evident from hundreds of chat logs between Google and SpamIt co-founder Dmitry “Saintd” Stupin. The conversations were part of thousands of hours of logs obtained by Russian cybercrime investigators who examined Stupin’s computer. The chats were later leaked online, and provide a rare glimpse into the day-to-day operations of Cutwail from the botmaster’s perspective. They also provide tantalizing clues as to the real-life identity of Google and his co-workers. Snippets of those conversations appear below, translated from their original Russian into English by native Russian speakers.

THE CUTWAIL MACHINE

Some of the best techical analysis of Cutwail came earlier this year in a paper from researchers at the University of California, Santa Barbara and Ruhr-University Bochum, which described in detail how the Cutwail botnet was operated, rented and promoted on the exclusive SpamIt forums. From their paper (PDF):

“The Cutwail spam engine is known in spam forums by the name 0bulk Psyche Evolution, where it is rented to a community of spam affiliates. These affiliates pay a fee to Cutwail botmasters in order to use their botnet infrastructure. In return, the clients are provided with access to a Web interface (available in Russian or English language) that simplifies the process of creating and managing spam campaigns…”

SpamIt affiliate records show that Google registered with the program using the email address psyche.evolution@gmail.com(according to historical WHOIS records, the domain name psyche-evolution.com was registered in 2005 by that same email address, to an organizations called “0bulk corp.” in Moscow).

In several chats with Stupin, Google describes how he and his pals switched to pharmacy spamming when promoting stocks via spam became less lucrative. In a discussion on Feb. 25, 2007, Google said he was “renting software for spam,” to competing spam affiliate programs “Mailien,” “Bulker,” and “Aff Connection,” and that all of his clients had great success converting traffic into sales. “We have been spamming stocks, however now stocks started converting badly, so we decided to spam in parallel with some affiliate programs. We organized people, gave them tasks to do. We’ve been spamming them for a week only, but I think we’ll do good.”

Last week, not long after I published the latest installment in my Pharma Wars series, KrebsOnSecurity.com was the target of a sustained distributed denial-of-service (DDoS) attack that caused the site to be unavailable for some readers between Nov. 17 and 18. What follows are some details about that attack, and how it compares to previous intimidation attempts.

The DDoS was caused by incessant, garbage requests from more than 20,000+ PCs around the globe infected with malware that allows criminals to control them remotely for nefarious purposes. If you’ve noticed that a few of the features on this site haven’t worked as usual these past few days, now you know why. Thanks for your patience.

I shared the log files of the attack with Joe Stewart, director of malware research at Dell SecureWorks. Stewart discovered that the botnet responsible for hitting my site appears to have been created with Russkill, a commercial crimeware kit that is sold for a few hundred bucks on the hacker underground. Russkill, sometimes called Dirt Jumper, does its dirty work by forcing infected systems to rapidly request the targeted site’s homepage.

Stewart said he suspects — but can’t prove – that the control center for this botnet is noteye.biz, based on traffic analysis of Internet addresses in the logs I shared with him.

“I did not already have [noteye.biz] under monitoring so it is impossible to say for sure what targets were hit in the past,” Stewart wrote in an email. He noted that the same attacker also apparently runs a Dirt Jumper botnet at xzrw1q.com, which also is currently attacking Ukrainian news site genshtab.censor.net.ua, and kidala.info (“kidala” is Russian slang for “criminal,” and kidala.info is a well-known Russian crime forum).

“According to my logs this botnet did attack your site back in April, so this is some additional circumstantial evidence that suggests the noteye.biz [control network] may have been involved in the recent attack on your site,” Stewart wrote.

As Stewart notes, this is not the first time my site has been pilloried, although it was arguably the most disruptive. In October 2010, a botnet typically used to spread spam for rogue Internet pharmacies attacked krebsonsecurity.com, using a hacked Linux server at a research lab at Microsoft, of all places.

I’ve spoken at more than a dozen events this year, and the same question nearly always comes up: Do you ever get threatened or attacked? For the most part, the majority of the threats or intimidation attempts have been light-hearted.

Yes, occasionally crooks in the underground will get a bit carried away – as in these relatedthreads from an exclusive crime forum, where I am declared the “enemy of carding;” or in the love I received from the guys at Crutop.nu, a major Russian adult Webmaster forum (the site now lives at Crutop.eu).

First, the good news: The past year has witnessed the decimation of spam volume, the arrests of several key hackers, and the high-profile takedowns of some of the Web’s most notorious botnets. The bad news? The crooks behind these huge crime machines are fighting back — devising new approaches designed to resist even the most energetic takedown efforts.

The volume of junk email flooding inboxes each day is way down from a year ago, as much as a 90 percent decrease according to some estimates. Symantecreports that spam volumes hit their high mark in July 2010, when junk email purveyors were blasting in excess of 225 billion spam messages per day. The company says daily spam volumes now hover between 25 and 50 billion missives daily. Anti-spam experts from Cisco Systems are tracking a similarly precipitous decline, from 300 billion per day in June 2010 to just 40 billion in June 2011.

There may be many reasons for the drop in junk email volumes, but it would be a mistake to downplay efforts by law enforcement officials and security experts. In the past year, authorities have taken down some of the biggest botnets and apprehended several top botmasters. Most recently, the FBI worked with dozens of ISPs to kneecap the Coreflood botnet. In April, Microsoft launched an apparently successful sneak attack against Rustock, a botnet once responsible for sending 40 percent of all junk email.

But botmasters are not idly standing by while their industry is dismantled. Analysts from Kaspersky Lab this week published research on a new version of the TDSS malware (a.k.a. TDL), a sophisticated malicious code family that includes a powerful rootkit component that compromises PCs below the operating system level, making it extremely challenging to detect and remove. The latest version of TDSS — dubbed TDL-4 — has already infected 4.5 million PCs; it uses a custom encryption scheme that makes it difficult for security experts to analyze traffic between hijacked PCs and botnet controllers. TDL-4 control networks also send out instructions to infected PCs using a peer-to-peer network that includes multiple failsafe mechanisms.

Spam trackers are seeing a fairly dramatic drop in junk e-mail sent over the past few days, specifically spam relayed by one of the world’s largest spam botnets – although security experts disagree on exactly which botnet may be throttling back or experiencing problems.

According to M86 Security Labs, the volume of spam has dipped quite a bit, approximately 40 percent since the beginning of the month by the looks of the graphic the company publishes on its site (pictured at right).

M86 says the decrease in spam is due to a rapid drop in activity from the Rustock botnet (see graphic below left), a collection of spam-spewing zombie PCs that experts say is responsible for relaying about 40 percent of all junk e-mail on any given day.

Bradley Anstis, vice president of technical strategy for M86, said the most likely explanation is that the person(s) operating Rustock rented the botnet to a number of spamit.com affiliates, and many of those affiliates have not yet switched over to another pharmacy affiliate program.

“To me, that’s the most logical explanation,” Anstis said. “The timing certainly hooks up well, because we started seeing this decline right around the first of October.”

Security researchers have dealt a mighty blow to a spam botnet known as Pushdo, a massive grouping of hacked PCs that until recently was responsible for sending more than 10 percent of all junk e-mail worldwide.

According to security firm M86 Security Labs, junk e-mail being relayed by Pushdo (a.k.a. Cutwail) tapered off from a torrent to a dribble over the past few days. M86 credits researchers at LastLine Inc., a security firm made up of professors and graduate students from University of California, Santa Barbara, the Vienna University of Technology (Austria), Eurecom (France), and Ruhr-University Bochum (Germany).

LastLine’s Thorsten Holz said his group identified 30 Internet servers used to control the Pushdo/Cutwail infrastructure, located at eight different hosting providers around the globe. Holz said Lastline contacted all hosting providers and worked with them to take down the machines, which lead to the takedown of nearly 20 of those control servers.

“Unfortunately, not all providers were responsive and thus several command & control servers are still online at this point,” Holz wrote on the company’s blog. “Nevertheless, this effort had an impact on Pushdo/Cutwail, which you can also see in new Anubisreports generated today by re-running the analysis: Many connection attempts fail and infected machines can not receive commands anymore.”